全文获取类型
收费全文 | 143665篇 |
免费 | 11736篇 |
国内免费 | 6083篇 |
专业分类
电工技术 | 8084篇 |
技术理论 | 10篇 |
综合类 | 10337篇 |
化学工业 | 24716篇 |
金属工艺 | 7477篇 |
机械仪表 | 8489篇 |
建筑科学 | 11415篇 |
矿业工程 | 3424篇 |
能源动力 | 3773篇 |
轻工业 | 12349篇 |
水利工程 | 2691篇 |
石油天然气 | 6642篇 |
武器工业 | 1056篇 |
无线电 | 16586篇 |
一般工业技术 | 16891篇 |
冶金工业 | 6784篇 |
原子能技术 | 1396篇 |
自动化技术 | 19364篇 |
出版年
2024年 | 612篇 |
2023年 | 2247篇 |
2022年 | 4206篇 |
2021年 | 5481篇 |
2020年 | 4192篇 |
2019年 | 3514篇 |
2018年 | 3800篇 |
2017年 | 4274篇 |
2016年 | 4006篇 |
2015年 | 5321篇 |
2014年 | 7198篇 |
2013年 | 8656篇 |
2012年 | 9409篇 |
2011年 | 10150篇 |
2010年 | 9166篇 |
2009年 | 8815篇 |
2008年 | 8640篇 |
2007年 | 8247篇 |
2006年 | 8240篇 |
2005年 | 7007篇 |
2004年 | 4859篇 |
2003年 | 4158篇 |
2002年 | 3906篇 |
2001年 | 3444篇 |
2000年 | 3390篇 |
1999年 | 3334篇 |
1998年 | 2898篇 |
1997年 | 2257篇 |
1996年 | 2109篇 |
1995年 | 1743篇 |
1994年 | 1412篇 |
1993年 | 1024篇 |
1992年 | 765篇 |
1991年 | 642篇 |
1990年 | 470篇 |
1989年 | 424篇 |
1988年 | 374篇 |
1987年 | 208篇 |
1986年 | 187篇 |
1985年 | 132篇 |
1984年 | 108篇 |
1983年 | 73篇 |
1982年 | 69篇 |
1981年 | 56篇 |
1980年 | 54篇 |
1979年 | 42篇 |
1978年 | 15篇 |
1977年 | 33篇 |
1976年 | 20篇 |
1975年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A new non-heating technique was developed for the sterilization of food stuff. Applying a roller compactor, ultra-high pressure sterilization has experimentally demonstrated its ability to sterilize dry powders, such as corn flour and Chinese herbs, with little quality deterioration. Also, the degree of food sterilization was found correlated well with the linear press forces between the rollers, roller gaps, and number of compaction passes. In comparison to the conventional high pressure sterilization technique, the new dry continuous processing method has the advantage of lower investment cost and is more versatile for sterilizing various food powders. 相似文献
992.
Free‐radical grafting of acrylic acid (AAc) onto isotactic polypropylene (iPP) using styrene (St) as a comonomer in supercritical carbon dioxide (SCCO2) medium was studied. The effects of temperature and pressure of reaction on functionalization degree (grafting degree of AAc) of the products were analyzed. The increase of reaction temperature increases the diffusion of monomers and radicals in the disperse reaction system of SCCO2. In addition, the increase of temperature accelerates the decomposition rate of 2,2′‐azobisisobutyronitrile (AIBN), thus promoting grafting reaction. It was also observed that functionalization degree of the products decreases with the increase of pressure of SCCO2 in the range of experiment. The effects of comonomer St on the functionalization degree of the products were investigated. The AAc graft degree of the resulting polymer was drastically higher in the present of St. It reached a maximum when the mass ratio of St and AAc was about 0.7 : 1. Because AAc is not sufficiently reactive toward iPP macroradicals, it would be helpful to use a second monomer that can react with them much faster than AAc. St preferentially reacts with the iPP macroradicals to form more stable styrene macroradicals, which then copolymerize with AAc to form branches. The highest functionalization degree was obtained when the AIBN was 0.75 wt %. When the initiator was used excessively, the functionalization degree decreased because of severe chain degradation of the iPP backbone. The morphologies of pure iPP and grafted iPP are different under the polarizing optical microscope. The diameter of the pure iPP spherulites is 20–38 μ and that of the grafted iPP spherulites is reduced with the increase of the functionalization degree of the products. This is proposed to be because the polar grafts formed during the reaction would have a tendency to associate in the hydrophobic PP environment. This might preserve some of the local crystalline order that existed during the reaction in the swollen iPP phase. It can be proven by a DSC cooling investigation that the crystallization temperature increased as the functionalization degree increased. This is proposed to be because the side‐chain of grafting polymer helps to bring about the heterogeneous nucleation in grafting polymer. Therefore, a large number of nuclei can emerge to a lesser supercooling degree. It can be also proven that the percent crystallization decreased as the functionalization degree increased, probably due to the grafted branches, which disrupted the regularity of the chain structure and increased the spacing between the chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2203–2210, 2004 相似文献
993.
994.
995.
多方法评价较单一方法更科学、可靠,可以丰富水资源评价的理论,利用熵值法、模糊物元法、非负矩阵对黄藏寺水库运行方案进行综合评价,三种方法结果的一致性为0.57,评价结果基本一致,利用序号总和理论,得到黄藏寺水库运行最优方案是方案12。多方法评价可以克服单一方法的局限性,较单一方法更可靠。 相似文献
996.
A direct method for evaluating equilibrium vapor compositions from measurements of the vapor pres-sure or boiling point of the solutions is presented.The basic differential equations are derived from Gibbs-Duhem equation and can be solved easily by iterative method.This method can be successfully used forbinary systems,and in principle can also be applied to multicomponent systems.Several examples ofbinaries and ternaries are presented for demonstration.Calculated results are in good agreement with ex-perimental data. 相似文献
997.
Chaoite-like carbon was prepared by quenching the pyrolysate of acetylene gas at 873 K and ambient pressure. Its morphology is carbon macrotubes (CMTs) with 20–60 μm in diameter and up to 8 mm in length. Microstructure analysis revealed that sp-bonded carbon (SPBC) chains in CMTs are kinked and the crystal orientation is anisotropic along the length and circumference directions of CMTs. A SPBC belt scrolling model was proposed for explaining the formation process of CMTs. 相似文献
998.
999.
Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to study the miscibility of blends of a graft copolymer of poly(methyl methacrylate) on linear low density polyethylene (LLDPE-g-PMMA, G-3) with poly(vinylidene fluoride) 1 Systematic name: poly(1,1-difluoroethylene). (PVF2) and the compatibilization of blends of LLDPE/PVF2. The specific interaction between PMMA side chains and PVF2 in G-3/PVF2 binary blends is weaker than that between the homopolymers PMMA and PVF2. There are two states of PVF2 in the melt of a G-3/PVF2 (60/40, w/w) blend, one as pure PVF2 and the other interacting with PMMA side chains. The miscibility between PMMA side chains and PVF2 affects the crystallization of PVF2. LLDPE-g-PMMA was demonstrated to be a good compatibilizer in LLDPE/PVF2 blends, improving the interfacial adhesion and dispersion in the latter. Diffusion of PMMA side chains into PVF2 in the interfacial region reduces the crystallization rate and lowers the melting point (Tm) and the crystallization temperature (Tc) of PVF2 in the blends. 相似文献
1000.
本文简述了在双氧水生产装置上应用变频调速技术对物料输送系统改造,实现有效节省能耗,降低生产成本,提高生产效率。 相似文献